composefs-native/boot: Handle systemd-boot and grub #1571

Johan-Liebert1 · 2025-09-01T11:55:17Z

Fix Grub boot error caused by #1541. Introduce a --bootloader cli option to --composefs-native. Depending upon the type of bootloader passed in we write BLS configs respectively

Signed-off-by: Pragyan Poudyal <[email protected]> Signed-off-by: Colin Walters <[email protected]>

Signed-off-by: Colin Walters <[email protected]>

Parse the Grub menuentry file, `boot/grub2/user.cfg` to get a list of bootable UKIs and figure out if a rollback is currently queued. Signed-off-by: Johan-Liebert1 <[email protected]>

Returning a local reference to a `&str` is quite tricky with rust. Update `title` and `chainloader`, the two dynamic fields in the grub menuentry, to be `String` instead of `&str` Signed-off-by: Johan-Liebert1 <[email protected]>

We parse the grub menuentries, get the rollback deployment then perform the rollback, which basically consists of writing a new .staged menuentry file then atomically swapping the staged and the current menuentry. Rollback while there is a staged deployment is still to be handled. Signed-off-by: Johan-Liebert1 <[email protected]>

…iles Signed-off-by: Johan-Liebert1 <[email protected]>

If two deployments have the same VMLinuz + Initrd then, we can use the same binaries for both the deployments. Before writing the BLS entries to disk we calculate the SHA256Sum of VMLinuz + Initrd combo, then test if any other deployment has the same SHA256Sum for the binaries. Store the hash in the origin file under `boot -> hash` for future lookups. Signed-off-by: Johan-Liebert1 <[email protected]>

Signed-off-by: Johan-Liebert1 <[email protected]>

Centralize all constants in a separate file Signed-off-by: Johan-Liebert1 <[email protected]>

Instead of `/sysroot/state/os/fedora` use `/sysroot/state/os/default` as the default state directory. Signed-off-by: Johan-Liebert1 <[email protected]>

Signed-off-by: Johan-Liebert1 <[email protected]>

Instaed of writing all present menuentries, only write the menuentry for switch/upgrade and the menuentry for the currently booted deployment. Signed-off-by: Johan-Liebert1 <[email protected]>

Signed-off-by: Johan-Liebert1 <[email protected]>

This allows for easier testing Signed-off-by: Pragyan Poudyal <[email protected]>

Add tests for functions `get_sorted_bls_boot_entries` and `get_sorted_uki_boot_entries` Signed-off-by: Pragyan Poudyal <[email protected]>

Just reducing code here.

Signed-off-by: Colin Walters <[email protected]>

The duplication between this and composefs-boot is high and we need to squash it; an important step there would probably be lowering the karg parsing. Signed-off-by: Colin Walters <[email protected]>

Signed-off-by: Robert Sturla <[email protected]> install: create temporary directory for ESP bls mount Plus additional review comments: - Created constant for EFI/LINUX - Switched from Task to Command - Create efi_dir as Utf8PathBuf Signed-off-by: Robert Sturla <[email protected]>

- Use `read_file` from `composefs::fs` - Always define `mod parsers` - Re-alphabetize/group module definitions Signed-off-by: John Eckersberg <[email protected]>

Fill `version` field in generated BLS config Signed-off-by: Johan-Liebert1 <[email protected]>

composefs/install/bls: Fix empty version in config

For bind mounting /etc we copy the contents of the EROFS' /etc to the deployment's state directory Mounting the EORFS requires help from the initramfs crate, so we also turn it into a library crate. Signed-off-by: Johan-Liebert1 <[email protected]>

composefs/install: Copy /etc contents to state

gemini-code-assist

Code Review

This pull request introduces support for both systemd-boot and grub by adding a --bootloader option, which is a great enhancement. The changes are well-structured, particularly the use of the BLSEntryPath struct to handle bootloader-specific paths. I've identified a critical issue with temporary directory handling that could lead to resource leaks, and a high-severity issue regarding backward compatibility for existing deployments. Addressing these will make the implementation more robust.

crates/lib/src/install.rs

crates/lib/src/status.rs

Fix Grub boot error caused by bootc-dev#1541. Introduce a `--bootloader` cli option to `--composefs-native`. Depending upon the type of bootloader passed in we write BLS configs respectively Signed-off-by: Johan-Liebert1 <[email protected]> Add guard again tempdir drop Signed-off-by: Johan-Liebert1 <[email protected]>

p5 · 2025-09-01T13:13:43Z

crates/lib/src/install.rs

            } else {
-                write_bls_boot_entries_to_disk(&efi_dir, id, usr_lib_modules_vmlinuz, &repo)?;
+                write_bls_boot_entries_to_disk(


Apologies for breaking GRUB in the previous PR. From reading through various docs (Fedora change requests) and issues in the repo, it sounded like GRUB was able to work in a (mostly) BLS-compliant way. My understanding must have not been correct.

I also think my understanding was further enforced through the function names - write_**bls**_boot_... - which made me think we were trying to achieve full BLS compliance in the Composefs backend.

I greatly appreciate you fixing the implementation rather than reverting the PR!

Grub doesn't fully support the BLS spec, that's why we have to jump over hoops to support it, which is unfortunate.

I greatly appreciate you fixing the implementation rather than reverting the PR!

We want to support systemd-boot eventually :)

cgwalters · 2025-09-02T22:42:46Z

crates/lib/src/composefs_consts.rs

@@ -19,6 +19,8 @@ pub(crate) const ORIGIN_KEY_BOOT: &str = "boot";
 pub(crate) const ORIGIN_KEY_BOOT_TYPE: &str = "boot_type";
 /// Key to store the SHA256 sum of vmlinuz + initrd for a deployment
 pub(crate) const ORIGIN_KEY_BOOT_DIGEST: &str = "digest";
+/// Bootloader, Grub or Systemd
+pub(crate) const ORIGIN_KEY_BOOTLOADER: &str = "bootloader";


We can very reliably detect if systemd-boot is in use by looking at the EFI variables it sets, or parsing bootctl --json or so...I'm not excited by carrying a stateful thing for this.

Also this heavily overlaps with what bootupd is doing. For the bootupd case of course since it installs the bootloader it may need some explicit configuration.

This heavily relates to my comment in ostreedev/ostree#3359 (comment)

Basically though, since we require bootc to manage some out of band config files for grub, how about we default to systemd boot, but query /boot and if we detect our own grub config files then we use that?

If we did need a config knob, see also #1532 which changed the install config.

how about we default to systemd boot,

Really I mean, default to the Boot Loader Spec...and detect grub by looking for the config files we currently need.

So the enum would be

enum Bootloader { BLS, Grub }

or so

It makes sense to default to systemd when we have full support for it in bootupd. Right now, since we don't have it, I think it makes sense to keep Grub as the default. When we do have full support, it's just a matter of updating the code to change the default

Making it stateless is definitely cleaner than relying on the origin file.

Making it stateless is definitely cleaner than relying on the origin file.

Right, can we do that here please?

Johan-Liebert1 and others added 26 commits August 29, 2025 17:05

WIP: composefs backend

2bd9e4c

Signed-off-by: Pragyan Poudyal <[email protected]> Signed-off-by: Colin Walters <[email protected]>

Rework composefs_booted to use kernel cmdline

c45dab5

Signed-off-by: Colin Walters <[email protected]>

composefs/status: Read UKI entries to check for queued rollback

d562f07

Parse the Grub menuentry file, `boot/grub2/user.cfg` to get a list of bootable UKIs and figure out if a rollback is currently queued. Signed-off-by: Johan-Liebert1 <[email protected]>

parser/grub: Use String instead of &str

839b858

Returning a local reference to a `&str` is quite tricky with rust. Update `title` and `chainloader`, the two dynamic fields in the grub menuentry, to be `String` instead of `&str` Signed-off-by: Johan-Liebert1 <[email protected]>

composefs/state: Use atomic writes for origin and staged deployment f…

e95af76

…iles Signed-off-by: Johan-Liebert1 <[email protected]>

parser/bls: impl Display for BLSConfig

7e05aa6

Signed-off-by: Johan-Liebert1 <[email protected]>

lib/composefs: Centralize constants

a6bcfbe

Centralize all constants in a separate file Signed-off-by: Johan-Liebert1 <[email protected]>

composefs/state: Name state directory default

f2d77c1

Instead of `/sysroot/state/os/fedora` use `/sysroot/state/os/default` as the default state directory. Signed-off-by: Johan-Liebert1 <[email protected]>

parser/bls: Add tests for bls parser

1425225

Signed-off-by: Johan-Liebert1 <[email protected]>

install/composefs/uki: Write only staged + booted menuentry on upgrade

e9206ff

Instaed of writing all present menuentries, only write the menuentry for switch/upgrade and the menuentry for the currently booted deployment. Signed-off-by: Johan-Liebert1 <[email protected]>

rollback/composefs: Print whether we are reverting the queued rollback

64f5ec3

Signed-off-by: Johan-Liebert1 <[email protected]>

refactor: Pass boot dir to boot entry readers

f3ab5b3

This allows for easier testing Signed-off-by: Pragyan Poudyal <[email protected]>

test: Add tests for reading boot entries

f65d5dd

Add tests for functions `get_sorted_bls_boot_entries` and `get_sorted_uki_boot_entries` Signed-off-by: Pragyan Poudyal <[email protected]>

Drop duplicate bls_config

0fb6edd

install: Use read_file from composefs-boot

01bade0

Just reducing code here.

install: Fix cargo fmt

7435396

Signed-off-by: Colin Walters <[email protected]>

status: Use constant for composefs

a324f58

Signed-off-by: Colin Walters <[email protected]>

status: Enhance composefs cmdline parsing to handle ?

705eaf8

The duplication between this and composefs-boot is high and we need to squash it; an important step there would probably be lowering the karg parsing. Signed-off-by: Colin Walters <[email protected]>

Post-rebase fixups:

b45ef30

- Use `read_file` from `composefs::fs` - Always define `mod parsers` - Re-alphabetize/group module definitions Signed-off-by: John Eckersberg <[email protected]>

composefs/install/bls: Fix empty version in config

a8313cb

Fill `version` field in generated BLS config Signed-off-by: Johan-Liebert1 <[email protected]>

Merge pull request bootc-dev#1558 from Johan-Liebert1/bls-version-fix

d7adf7d

composefs/install/bls: Fix empty version in config

Merge pull request bootc-dev#1560 from Johan-Liebert1/bind-mnt-etc

fd703ec

composefs/install: Copy /etc contents to state

bootc-bot bot requested a review from cgwalters September 1, 2025 11:55

gemini-code-assist bot reviewed Sep 1, 2025

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Johan-Liebert1 force-pushed the grub-bls-fix branch from f0e8700 to 6362c43 Compare September 1, 2025 12:25

p5 reviewed Sep 1, 2025

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cgwalters requested changes Sep 2, 2025

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jeckersb force-pushed the composefs-backend branch from fd703ec to 023be10 Compare September 3, 2025 21:01

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